3770k at 4.4ghz (Using asrock tweaker that does it all for you)
GTX 770 Lightning Edition.
AsRock z77 extreme 4
Now those specs are pretty decent, i can max out pretty much every game out there, but even on lower settings and games where i can obtain 200fps, i get random lag spikes while just walking around with nothing epic happening. IT also seems to happen when i ADS.
The games i play generally are Dayz, BF3/4, CoD Ghosts, CS GO, ARMA 3.
It could be a coincidence because all these games seem to have massive problems, but i'm pretty sure i've even seen it happen while on youtube etc.
What do you think it could be? Slow HDD? the fact my CPU and GPU are OC'ed?
Take a step back. Whenever you have 'problems' like this it is best to start with MANUFACTURER settings first, THEN move up to any 'tweaks'. When purchased 'off the shelf' the exact way it is in 'the box' and the 'advertised performance' is only based on that 'in the box setting'. Once you establish that as your 'baseline' then anything you do (Asrock tweaker) and you see negative effects (lag spikes) indicates the 'threshhold' your hitting where more negative things will happen the more you 'push' in that direction. Normally people fine that 'threshhold' then dial it back 1 level too keep max performance AND minimal negative effect in equilibrium.
I would first try the same tests you did, same multiple games, only in Single Player Mode. Do you get spikes or not? Then I would test with the 'out of box' settings for Multiplayer (no tweaks to your system at all). Again do you get spikes or not?
If you didn't get spikes at all when 'out of the box' then I would suggest that is where you need to look at your PC settings as the issues.
If you get no spikes in SP mode, but even 'out of the box' you get spikes while in MP mode, then it is most likely NOT your PC but how that PC connects to those places (your little sister keeps watching MLP videos slowing things down at time when she 'switches' to a new video, etc.). Then you need to look at employing QoS on the Router and all 'devices' connecting to it (Iphones, PCs, Tablets, etc.).